It is known in the art to use steering sensors for controlling steering systems and suspension systems. Sensors of the fixed center type are prone to failure due to mis-adjustment of the sensor inasmuch as precise angular measurements must be obtainable from such sensors if they are to be useful in providing rapid response to a steering system event. These sensors must be installed and calibrated correctly at the time the vehicle is manufactured as well as requiring re-calibration whenever the steering system geometry is changed. The steering system geometry may be changed while the vehicle is in use, necessitating service to to calibrate the steering sensor.
To avoid these problems, relative steering sensors have been developed that are capable of measuring relative motion of the steering system, however, they must determine the actual or true center position of the steering system each time the vehicle is operated. Such a steering sensor is disclosed in U.S. Pat. No. 4,722,545, which is assigned to the assignee of the present invention. That system uses a software program in which steering center position is determined through the use of a variable sample time detection scheme operating with variably sized circumferential window zones of operation of a steering shaft. Because the sampling process associated with the algorithm of U.S. Pat. No. 4,722,545 cannot determine whether there are forces being applied to the steering system, the algorithm disclosed therein may be slow to converge on an accurate center position, especially when the vehicle is operated in nearly continuous, constant radius circles.
It would be desirable to provide a method and apparatus capable of rapidly determining an accurate or true center position of a steering system without requiring the expense and complexity of a fixed steering sensor.